Previously, an in-tank fuel supply device, which is placed in the inside of the fuel tank, is widely used at the internal combustion engine of a vehicle. In the device, which is disclosed in the patent literature 1 as this kind of fuel supply device, a coupling stay couples between a cover body, which is installed to an upper wall of the fuel tank, and a pump unit, which is placed on a bottom wall of the fuel tank and is operable to discharge the fuel from the inside of the fuel tank toward the internal combustion engine.
In the device disclosed in the patent literature 1, the coupling stay provides radial support and thrust support to the pump unit. Under this supporting state, a wall portion, which projects from the pump unit, can be fitted between a longitudinal bar, which projects from the coupling stay, and a projection of the coupling stay, to lock rotation of the pump unit about a rotational axis relative to the coupling stay. The rotation of the pump unit relative to the coupling stay is used at the time of inserting the fuel supply device into the inside of the fuel tank and thereby needs to be limited by the locking after the insertion of the fuel supply device into the inside of the fuel tank.
However, in the device disclosed in the patent literature 1, the fuel tank expands and contracts in response to repeating of operation and stop of the internal combustion engine. Therefore, the pump unit 101 and the cover body 102, which are schematically indicated in FIGS. 18(a) and 18(b), respectively follow the bottom wall 2c and the upper wall 2a of the fuel tank 2. Thereby, the pump unit 101 tries to tilt about an axis Ap, which crosses the rotational axis Ar, toward the coupling stay 100.
At this time, when a point Sf, at which a load is applied from the cover body 102 to the coupling stay 100, is defined as a point of effort Pe, a contact part Sc, at which a wall portion 103 projected from the pump unit 101 contacts the projection 104 of the coupling stay 100, forms a fulcrum Pp. Therefore, at a radial support part Sr, at which the pump unit 101 receives the radial support from a hole inner peripheral surface 100a of the coupling stay 100, a boundary Sb between a lateral surface 100b of the coupling stay 100, which provides the thrust support to the pump unit 101, and a hole inner peripheral surface 100a forms a point of load PI where a force is applied to the rotatable shaft portion 101a, as shown in FIG. 18(c). In FIG. 18(c), in order to ease the understanding of the description, only a part of the boundary Sb is indicated as the point of load PI.
Here, in the device disclosed in the patent literature 1, as illustrated in FIG. 18(a), the contact part Sc between the wall portion 103 and the projection 104 is assumed to be deviated related to the boundary Sb between the hole inner peripheral surface 100a and the lateral surface 100b at the radial support part Sr in a transverse direction along the rotational axis Ar. Specifically, the fulcrum Pp and the point of load PI are deviated from each other in the transverse direction. Therefore, the amount of displacement of the point of load PI about the fulcrum Pp is increased in response to the tilting of the pump unit 101. Furthermore, the contact part Sc extends to a location, which is higher than the rotational axis Ar in the longitudinal direction, so that the fulcrum Pp is placed to be closer to the point of effort Pe than the point of load PI. Therefore, a pulling force, which pulls the rotatable shaft portion 101a from the pump unit 101 side, becomes dominant at the point of load PI. Because of the above configuration, a breakage of the rotatable shaft portion 101a at the radial support part Sr may possibly occur, as illustrated in FIG. 18(b).